The Physics of Filtering

When I was small child, our family lived in house without air-conditioning. We had screens on all the windows and an attic fan to cool the house. The gaps in the screens were small enough to prevent flies and mosquitos from entering the house. It would have been foolish to replace the screens with chain link fencing and expect that the bugs would still be kept out. A housefly has a wing span around 1/2 lnch, and the wires in chain link fencing are a couple of inches apart. The gap is about four times the size of a fly. A fly can easily pass through.

The gap between fibers in a typical cloth face mask is on the order of 2 to 3 micrometers. The coronavirus is on the oder of 0.3 micrometers.

The mathematics of the filtering is left to the Gentle Reader as an exercise.

Meanwhile, in Iran …

… the coronavirus pandemic appears to have spread to all regions of that country. The BBC has this video posted with footage from social media showing a morgue in the city of Qom full of dead bodies to be tested for the coronavirus.

Totalitarian societies such as China and Iran have not done well in their public health responses to the virus. Neither have most countries with socialize medicine, e.g., Italy. Could it be that part of the reason for Bernie’s burnout in the last few primaries is that too many Democrats gat hurt by changes in their health insurance under Obamacare, and that the prospect of having the same sort of system as China has caused them to reconsider giving the leadership of their part to a Socialist?

Hmmmm.

UPDATE—

Coronavirus Notes

I haven’t posted as much as usual this week because I’m dealing with a nasty head cold, and, yes, it’s just a cold. However, i’ve seen a few things related to the coronavirus go by that are worth sharing.

One of the hot spots for the illness is Iran where many members of the ruling class have ti.

It looks as if Israel is among the leaders in development of a vaccine.

And the World Health Organization has declared that we are in a pandemic.

BTW, I was at CPAC a couple of weeks ago. According to the emails I’ve received from the event organizers, the Maryland State Health Department has screen all of the employees of the event venue, and none of them tested positive for corona virus. There were a couple of other events going on at the venue at the same time as CPAC. One was a medical meeting, and during my time in the Lobby Bar, I had an interesting conversation with an ophthalmologist about her preparations for dealing with the disease. Because her work require close patient contact, she plans to use additional layer of protective equipment—and she plans on additional screening of patients before they are seen. Her prime concerns were the availability of extra masks, gloves, etc., and whether the public would act calmly and responsibly in following medical advice (as opposed to press and political sensationalism).

The next few months will be interesting. (Say, is it raaaaacist to point out that old Chinese curse, “May you live in interesting times..”?)

Investment Opportunities

I make money in the stock market two ways. One way is buying stocks that pay dividends, and I hold those stocks long term as long as the dividends they pay are a good return on investment. The other way is buy stocks that I expect will appreciate in market value. I sell those stocks when I feel I can make a satisfactory profit. The recent coronavirus and Bernie scares that caused share prices to drop unreasonably was an opportunity to engage in that second method.

The DJIA is up over 5 % today.

Ka-ching!